Information storage medium, recording method used therefor and reproducing apparatus

ABSTRACT

Data on multiple stories or scenes are recorded on a recording medium so as to reduce the physical distance moved by a pickup at playback time and to suppress breaks or disturbances in reproduced video. A multi-scene program having a plurality of optionally selectable branch stories B0, B1, B2, B3, etc., is recorded between a branch point X and a connection point Y. The preceding main story of a video program, made up of video, sound, text and the like, branches off at branch point X to the branch stories, and at connection point Y connects to the succeeding main story in the video program. The recorded state between the branch point X and the connection point Y is such that the branch stories are each divided into multiple cells and the cells of the respective branch stories are recorded time-division multiplexed.

This is a division of application Ser. No. 08/780,432, filed Jan. 7,1997.

BACKGROUND OF THE INVENTION

The invention relates to an information recording method useful inrecording video, sound, subvideo, etc. on a recording medium, such as anoptical disk or the like, and a recording medium and a reproducingapparatus used with the method.

In recent years, optical disks on which video, sound, subvideo, etc. arerecorded have developed to record information at a high density.Playback apparatuses have been developed to retrieve the informationrecorded. In recording information, such as a movie, on an optical disk,it has been proposed to record story data for multiple stories thatproceed simultaneously. For example, suppose brothers A and B pursuetheir separate courses in, and life as they grow up one of them becomesa police officer (the first story), the other becomes a gangster (thesecond story), and after some time, they meet again and then get alongtogether. This is the type of story data used for multiple stories thatproceed simultaneously.

In addition, in recording information, such as a movie, on an opticaldisk, it has been proposed to record the same event is from multipleangles to produce simultaneously proceeding multi-angle scenes. Forexample, a multi-angle scene could have a first scene of a ship crossingover the ocean viewed from land and a second scene of the land viewedfrom the ship at the same time.

A producer has options of showing viewers the first and second storiesin combination, showing mainly the first story to viewers, or showingmainly the second story to viewers. However, in conventional movieproduction practices, one of the options must be chosen.

The same may be said of the first and second scenes. If viewers wereable to choose freely between the first and second stories or the firstand second scenes, the producer would have greater freedom in movieproduction.

In recent years, an optical disk and playback system has been developedin which multiple stories or multiple scenes that proceed simultaneouslyhave been recorded in advance and viewers are allowed to chose fromamong them.

It is preferable that multiple stories or scenes be recorded on anoptical disk in such a way that, at playback time, data will becomeconvenient to handle. Suppose that story data on first and secondstories are recorded serially. At playback time, only one of the storiesis reproduced, it is required to jump to a storage area for the other.However, if the other story is short, the physical movement of thepickup will be small, causing no problem. If, however, the other storyis lengthy, the physical movement of the pickup increases. For thisreason, a break or disturbance may occur during video playback.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide an information storagemedium on which multiple stories or multi-angle scenes are recorded insuch a way as to decrease the physical movement of a pickup at playbacktime and to supress any breaking or disturbance in the reproduced view,a recording method and a reproducing apparatus used with the storagemedium.

To attain this object, this invention is, in recording onto arecording/recorded medium a video program that allows a main story tobranch off into multiple branch scene and the branch scenes to connectto a succeeding main story, divides data on each of the branch scenesinto multiple scene cells and arranging the scene cells of therespective branch scenes on a time-division multiplexing basis.

By recording in this arrangement, the cells of the same branch scene arepicked up at playback time for data reproduction. Even in playing backany branch scene, the distance moved by the pickup is not great, thussuppressing breaks or disturbance in reproduced video.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention and, together with the general description given above andthe detailed description of the preferred embodiments given above; serveto explain the principles of the invention.

FIG. 1 is a diagram used to explain an embodiment of an informationrecording medium and a recording method of the invention.

FIG. 2A is a diagram used to explain an exemplary arrangement of cellsin FIG. 1 and an exemplary playback sequence thereof.

FIG. 2B is a diagram used to explain an exemplary arrangement of cellsin FIG. 1 and another exemplary playback sequence thereof.

FIG. 3A is a diagram for use explaining another embodiment of theinformation recording medium and the recording method of the invention.

FIG. 3B is a diagram for use in explaining still another embodiment ofthe information recording medium and the recording method of theinvention.

FIG. 4A illustrates a cell or cells to which each of the cells of FIG.3B is connected in the form of a table.

FIG. 4B illustrates an example of a specific arrangement of the cells ofFIG. 4A.

FIG. 5 is a diagram for use in explaining an exemplary arrangingalgorithm for the cells of FIG. 3B.

FIG. 6 is a diagram for use in explaining exemplary playback of thecells arranged as shown in FIG. 3B.

FIG. 7A is a diagram for use in explaining a further embodiment of theinformation recording medium and the recording method of the invention.

FIG. 7B illustrates an exemplary arrangement of the cells of FIG. 7A ona track.

FIG. 8A is a diagram for use in explaining a still further embodiment ofthe information recording medium and the recording method of theinvention.

FIG. 8B illustrates an exemplary arrangement of the cells of FIG. 8A ona track.

FIG. 9A is a diagram for use in explaining another embodiment of theinformation recording medium and the recording method of the invention.

FIG. 9B illustrates an exemplary arrangement of the cells of FIG. 9A ona track.

FIG. 10A is a diagram for use in explaining still another embodiment ofthe information recording medium and the recording method of theinvention.

FIG. 10B is a diagram for use in explaining a further embodiment of theinformation recording medium and the recording method of the invention.

FIGS. 11A, 11B and 11C are diagrams for use in explaining otherembodiments of the information recording medium and the recording methodof the invention.

FIG. 12 is a diagram of an exemplary arrangement of the cells of FIG.11C.

FIGS. 13A, 13B and 13C are diagrams for use in further explaining adividing method used in recording multiple stories on the recordingmedium of the invention.

FIG. 14 is a schematic illustration of a playback apparatus for use withthe recording medium of the invention.

FIG. 15 illustrates volume space on an optical disk to which theinvention is applied.

FIG. 16 illustrates the structures of the video manager (VMG) and thevideo title sets (VTS) in more detail.

FIG. 17 illustrates a relationship between video object set (VOBS) andcells and further illustrates the contents of the cells hierarchically.

FIG. 18 is a diagram for use in explanation of an example of controllingthe sequence in which the cells are played back by a program chain(PGC).

FIG. 19 illustrates a relationship between a video object unit (VOBU)and video packs in the unit.

FIG. 20 illustrates an exemplary arrangement of interleaved blocks.

FIG. 21 illustrates a recorded state in which video objects of angle-1and angle-2 scenes are arranged on one track with each divided intothree interleaved units (ILVU11-1 to ILVU3-1, ILVU1-2 to ILVU3-2) and anexemplary playback output of the angle-1 scene.

FIG. 22 illustrates the optical disk playback apparatus,of FIG. 14 in asimplified form.

FIG. 23 is a diagram for use in explaining where an increase and adecrease in data entry into the track buffer at the time of playback ofinterleaved blocks the worst.

FIG. 24 is a diagram for use in explaining a decrease in data in thebuffer memory with time when a kickback operation is performed and amaximum jump is subsequently made in the playback apparatus.

FIG. 25 is a diagram for use in explaining examples of designs of theminimum capacity (Bm) of the track buffer, the kickback and seek time,the jump distance, and the amount of output data per unit time from thetrack buffer in the playback apparatus.

FIG. 26 illustrates video title set information (VTSI) in a video titleset (VTS).

FIG. 27 illustrates the contents of a video title set program chaininformation table (VTS₋₋ PGCIT).

FIG. 28 illustrates the structure of program chain information (PGCI).

FIG. 29 illustrates cell playback information (C₋₋ PBIT) and thecontents thereof.

FIG. 30 illustrates the contents of a cell position information table(C₋₋ PSIT).

FIG. 31 illustrates the formats of a pack and a packet recorded on anoptical disk.

FIG. 32 illustrates an NV₋₋ PCK pack.

FIG. 33 illustrates information described in the data search generalinformation (DSI₋₋ GI).

FIG. 34 illustrates information described in the seamless playbackinformation (SML₋₋ AGLI).

FIG. 35 illustrates the contents of the seamless angle information(SML₋₋ AGLI).

FIG. 36 illustrates the VOBU search information (VOBU₋₋ SRI).

FIG. 37 illustrates the synchronization information.

DETAILED DESCRIPTION OF THE INVENTION

(Preferred Embodiments)

Hereinafter, the embodiments of the invention will be described withreference to the drawings.

FIG. 1 illustrates the flow of a video program on time axis for thepurpose of describing an embodiment of the invention. This video programhas a preceding main story (or scene) A, multiple branch stories B0 toB3, and a succeeding main story (or scene) C. The branch stories branchoff at a point X which is the final position in the preceding main storyA and join at a point Y of connection which is the initial point of thesucceeding main story C. Here, the preceding main story, the branchstories and the succeeding main story in the video program are eachdivided into multiple scene cells. The cells of the branch story B0 arerepresented as B0-5, B0-4, . . . , B0-1, the cells of the branch storyB1 as B1-2 and B1-1, the cells of the branch story B2 as B2-5, B2-4, . .. , and B2-1, and the cells of the branch story B3 as B3-5, B3-4, . . ., and B3-1.

One scene cell can be defined by various methods which will be describedbelow.

For example, one scene cell may be defined with the physical length of atrack on the recording medium taken as a unit, and any scene cell is setto be equal in length. Also, one scene cell may be defined with thelength of time for playback taken as a unit, and any scene is set equalin playback time. When data is encoded, one scene cell may be defined asthe amount of coding. Any scene cell is set equal in the amount ofcoding. In any definition, scene cells need not to be strictly set equalin length or amount, and it is required only that they be substantiallyequal to each other.

When there are multiple branch stories as described above which arerecorded on a recording medium, each of the branch stories is arrangedso that its scene cells will appear at the same rate relative to the sumof scene lengths of the branch stories. In the example of FIG. 1, thereare four branch stories, and the 0-th branch story contains five scenecells, the first branch story contains two scene cells, and the secondand third branch stories each have five scene cells. The sum of scenelengths is 17 cells. Thus, the 0-th, second and third branch stories areeach arranged at a rate of 5/17, i.e., at a rate of one for about 3.5cells. The 0-th branch story is arranged at a rate of 2/17, i.e., at arate of one for 8.5 cells.

With such an arrangement, as shown by the recording arrangement of cellsof FIG. 1, the jump interval when the first branch story is particularlyplayed back becomes smaller than that which would be formed if thesecond branch story were arranged aggregated.

FIG. 2A illustrates the pickup interval for the 0-th branch story (solidarrows), the pickup interval for the third branch story (broken arrows),and the pickup interval for the first branch story (dashed-and-dottedarrows) in the above-described arrangement pattern.

FIG. 2B, on the other hand, illustrates the pickup interval for the 0-thbranch story (solid arrows), the pickup interval for the third branchstory (broken arrows), and the pickup interval for the first branchstory (dashed-and-dotted arrows) in the case where each branch story isarranged in sequence. With such an arrangement, the pickup intervalbecomes very long, increasing the risk of a break or disturbance duringthe video playback. With an arrangement of the invention, however, sucha pattern as shown in FIG. 2A can be obtained, in which the pickupinterval is narrowed, thereby suppressing a break or disturbance inreproduced video.

Next, arranging scene cells after scene cells of each branch story havebeen determined will be described.

Suppose now that there is a video program that has multiple branchstories (including multi-angle scenes) as shown in FIG. 3A. Multi-anglescenes refer to simultaneously proceeding videos that are shot fromdifferent angles, such as a video of a conductor shot close-up in aconcert hall and a video of the whole orchestra shot from the seats inthe hall.

In FIG. 3A, A0 is a preceding main scene, B0 is a dummy branch scene,and B1 and B2 are branch stories having different contents. This videoprogram is divided into scene cells as shown in FIG. 3B. Each scene cellis marked with data capacity and given a cell number. Each of point ofdivision, which is indicated by a black dot, serves as the beginningpoint of a video frame. In this example, the data playback time is setequal for all scene cells. The data is variably compressed data. Thus,even if the playback time is the same for all scene cells, the datacapacity is not necessarily the same for all scene cells. In FIG. 3B,although B0 is indicated by one black dot, it is a dummy story andsupposed to have no actual data.

When the scene cells are set in the above manner, a table L1 is set up,which indicates the cell number or numbers of a scene cell or cells towhich each scene cell is connected as shown in FIG. 4A. That is, thescene cell number connected to the scene cell number A0-1 is A0-0 only.The cell number connected to the cell number A0-0 is B1-3 or B2-2 orC0-0, or C1-0. If each scene cell is associated in this way with a scenecell or cells to which it is connected, the table L1 shown in FIG. 4Acan be obtained.

FIG. 4B is a cell-number table L2 set up to actually arrange each scenecell serially on a track of a recording medium on the basis of theinformation in the table of FIG. 4A.

Next, to actually arrange each scene cell serially on a track of arecording medium on the basis of the information in which a scene cellor cells to which each scene cell is connected, i.e., to obtain anarrangement in table L2, the order of arrangement is determined by thefollowing procedure.

FIG. 5 shows an algorithm for determining the order in which cellnumbers are arranged.

First, the cell number and the capacity on the first row in table L1 iswritten into the first row in table L2 (steps S1 and S2). The cellnumber to which the cell is connected is also read. Next, a decision ismade as to whether all the cell numbers to which the associated cellnumber of cell numbers to which no connection completion flag isattached in table L2 is connected lie within the maximum allowable jumprange (Jmax) in the forward and backward directions with respect to itscell number position.

The maximum allowable jump range (Jmax) is a value that is determined bythe response speed of a pickup used in playback apparatus and thecapacity (reproducing time) of an output buffer which temporarily storesdata to be output for playback.

With the relationship between the cell number A0-1 and the cell numberA0-0 to which A0-1 is connected, the Jmax (20 Mb in this example) ismet. Thus, a connection completion flag is attached to the row for A0-1in table L2 (step S4). Next, from table Li are read the cell numberA0-0, its data capacity, and the cell numbers B1-3, B2-2, C0-0 and C1-0to which A0-0 is connected (step S3).

A decision is made as to whether all the cell numbers to which theassociated cell number, of cell numbers A0-0, B1-3, B2-2, C0-0 and C1-0to which no connection completion flag is attached, is connected fallwithin the maximum allowable jump range (Jmax) in the forward andbackward directions with respect to its cell number position. In thiscase, the distances between A0-0 and C0-0 and between A0-0 and C1-0exceed Jmax, so that the procedure goes to step S6 via step S5.

Step S5 makes a decision as to whether the number of cell numbers towhich no connection completion flag is attached is only one and the cellnumber or numbers to which that cell number is present or absent and isone for the final decision of the completion of arrangement processing.

Since the arrangement is not completed at the time the cell number A0-0was read, the procedure goes to step S6. In step S6, use is made of thecell number A0-0 and the cell numbers B1-3, B2-2, C0-0 and C1-0 to whichthe cell number A0-0 is connected to make the following decision. Thatis, with the assumption that a scene cell number is represented by $m-n,one in which $ is minimal and is selected first. In this example, thereare B and C and hence B is selected (in this example it is assumed thatA<B<C). Further, a situation in which n is maximal and m is minimal isextracted. That is, that n is large means that the number of divisionsis large, and that m is small means that the priority assigned to abranch story is high.

In the above example, as can be seen from FIG. 3B, the scene cell numberfollowing A0-0 is B1-3. Next, the cell number B1-2 to which the cellnumber B1-3 thus extracted is connected is provisionally arranged on thelast row in table L2 (step S7). It is B1-2 that follows B1-3. Thus, cellarrangement is in the order of A0-0, B1-3, B2-2, C0-0, C1-0, and B1-2.

Next, with all of cells to which other cell numbers (B2-2, C0-0, C1-0)than the extracted cell number B1-3 which have not been connected yetare connected being provisionally arranged to follow, a decision is madeas to whether the distances in amount of coding between the cell numberswhich have not been connected yet and the cells to which they areconnected are all below Jmax (20 Mb) (step S8). In this example, B2-1,D0-0, D1-0, D0-0 and D1-0 will be further arranged to follow B2-2, C0-0,C1-0 and B1-2. In this case, the distance (the amount of coding) betweenB2-2 and B2-1, the distance between C0-0 and D0-0 and the distancebetween C1-0 and D1-0 are all within Jmax. As a result, it is determinedthat the provisional arrangement is normal and the procedure thenreturns to step S3 via step S11.

In step S3, the previous provisional arrangement contains B1-3, B2-2,C0-0, C1-0, and B1-2 and they have each been attached with a connectioncompletion flag as being normal. Thus, B2-1, D0-0, D1-0, D0-0 and D1-0are present as ones to which no connection completion flag is attached.

Next, suppose that, following B2-1, D0-0, D1-0, D0-0 and D1-0, the cellnumbers to which each of them is connected are arranged. That is, thecell numbers are arranged such that B2-1, D0-0, D1-0, D0-0, D1-0, B2-0,E0-0, E1-0, E0-0 and E1-0. In step S3, a decision is made as to whetherall the cell numbers to which a cell number (one that has been attachedwith no connection completion flag) is connected lie within the maximumallowable jump range (Jmax) in the forward and backward directions withrespect to that cell number. In this case, all the cell numbers areabove Jmax and hence the procedure goes to step S6. In step S6, B2-1 isextracted, and in step S7, B2-0 is taken out and B2-1, D0-0, D1-0, D0-0,D1-0 and B2-0 are arranged on the last row.

Next, in step S8 again, with all of cells to which the other cellnumbers (D0-0, D1-0, D0-0, D1-0, B2-0) than the extracted cell numberB2-1, which have not been connected yet, are connected beingprovisionally arranged to follow, a decision is made as to whether thedistances in amount of coding between the cell numbers which have notbeen connected yet and the cells to which they are connected are allbelow Jmax (20 Mb). That is, when E0-0, E1-0, E0-0, E1-0, C0-0 and C1-0are arranged to follow (D0-0, D1-0, D0-0, D1-0, B2-0), a decision ismade as to whether the distance between each of D0-0, D1-0 and B2-0 andthe cell number to which it is connected falls below 20 Mb. In thisexample, the distance between B2-0 and C0-0 and the distance betweenC1-0 exceed 20.

In this case, therefore, the procedure goes to step S9, in which adecision is made as to whether the number of cell numbers that do notmeet the conditions is two or more. When the number is two or more, itis assumed that an error has occurred. In this example, the number isone and the procedure goes to step S10.

In step S10, all the cells to which unconnected cells that have not beenconnected yet and that do not meet the conditions are arranged and thentheir cell number and coding amount are read (in this case, C0-0 andC1-0 are read).

A return is made from step S10 to step S6, in which a cell number isselected in accordance with the above-described principles. That is, thecell number $m-n is extracted in which $ is minimal, n is maximal, and mis minimal. The procedure then goes to steps S7 and S8.

As described above, according to the algorithm, each of the branchstories is divided by the amounts of coding that, for example, permit anequal playback time to be obtained and the order of arrangement isdetermined by the principles indicated in steps S3 and S6.

In FIG. 6 there are illustrated several playback examples in a disk onwhich a recording is made in accordance with an arrangement determinedas described above. Scene cells are picked up in the order indicated byarrows.

The above example is one example and the invention can be implemented invarious ways.

The dividing method shown in FIG. 3B can be modified in various ways.According to the above-described method of determining points ofdivision, each of branch stories is divided into multiple scene cells bythe amounts of coding that permit the playback time to be the same forall the cells of the branch stories, and the amounts of coding arereferenced to make a decision of whether the distance over which thepickup makes a jump lies within the maximum jumping amount Jmax inaccordance with the above-described algorithm.

However, in determining points of division, each branch story may bedivided separately.

FIG. 7 shows an example in which there are three branch stories and eachof the first, second and third stories is equally divided into threecells so that each cell will have an equal amount of coding. That is, asshown in FIG. 7A, the first branch story is separated into three cells,numbered B0-0, B0-1 and B0-2, each of an equal amount of coding (5 Mb),the second branch story is divided into three cells B1-0, B1-1 and B1-2each of an equal amount of coding (7 Mb), and the third story is dividedinto three cells B2-0, B2-1 and B2-2 each of an equal amount of coding(6 Mb). The number of divisions is the same for each branch story whichis three in this example.

With such division, when, as shown in FIG. 7B, a set of cells B0-0, B1-0and B2-0 is taken as scene cell block #0, a set of cells B0-1, B1-1 andB2-1 as scene cell block #1, and a set of cells B0-2, B1-2 and B2-2 asscene cell block #2, each scene cell block has an equal amount ofcoding.

The amount of coding (the amount of data) being equal means that thejumping distance is the same for playback of each of the branch streamsB0, B1, and B2.

In the above example, division is made by an equal amount of coding.However, each branch may be divided by an equal playback time.

FIG. 8 shows an example in which there are three branch stories and eachof the first, second and third stories is equally divided into threecells so that each cell will have an equal playback time. That is, asshown in FIG. 8A, the first branch story is separated into cellsnumbered B0-0, B0-1, B0-2, and B0-3 each of an equal playback time, thesecond branch story is divided into cells B1-0, B1-1, B1-2 and B1-3 eachof an equal playback time, and the third story is divided into cellsB2-0, B2-1, B2-2 and B2-3 each of an equal playback time.

In this case as well, as shown in FIG. 8B, scene cell blocks #0 to #3can be obtained.

In the above examples, the cell arrangement method for multiple storieswas described. The same method can be applied to the arrangement ofmulti-angle scenes. When one wants to watch pictures shot from adifferent angle from the middle, for example, when it is desired towatch pictures of the whole orchestra shot from seats in the concerthall in the middle of watching pictures of the conductor only shot inclose-up, he or she can watch freely pictures shot from different anglesif multi-angle pictures are recorded.

FIG. 9A shows multi-angle picture information. When a first angle sceneD0-0 to D0-3 and a second angle scene D1-0 to D1-3 exist as aninformation source, scene cell blocks #0 to #3 are formed and arrangedas shown in FIG. 9B by way of example.

FIG. 10 shows an example of a source when one of multiple stories endsin an extremely short time. FIG. 10B shows the case where each of thebranch stories is divided by a predetermined number (4) into cells.

Even if, when one of the branch stories is extremely short as describedabove, the cells of the story B0 and the cells of the other stories aresimply multiplexed together, the jump distance may become long when atransition is made from playback of the B0 story to playback of the nextC0 story, failing to satisfy the conditions.

To solve this problem, such a method as shown in FIG. 11A is used.First, as shown in FIG. 11A, a part of the succeeding main story C0 isadded to each of the branch stories B0, B1 and B2, and the point ofconnection is shifted backwards. The branch stories are then taken asB0(E), B1(E), and B2(E) as shown in FIG. 11B. Each of the branch storiesB0(E), B1(E) and B2(E) is divided into cells, which are numbered asshown in FIG. 11C. The method of subsequent arrangement is the same asthe procedure described previously. In this example, each branch storyis divided into five cells.

FIG. 12 shows the state in which cell blocks #0, #1, . . . are preparedand arranged, each block containing one cell selected from each branchstory. These scene cell blocks each contain an error correcting code. Inthis example, the scene cell blocks have the same amount of coding. Withcompressed data by the MPEG2 system in general, division is made so thatnon-compressed video data, i.e., I-picture or intra-frame compresseddata or data expandable without the use of other frame compressed data,is contained at the beginning of cells. This is because, in view of thecompression system, in the absence of non-compressed video data in theleading cell, succeeding compressed video data cannot be reproduced.

Reference will be made to FIGS. 13A to 13C to explain exemplary divisionof multiple stories mathematically in the case where they are recordeddivided.

As shown in FIG. 13A, suppose that a video program, composed of video,sound, text, etc., contains optionally selectable multiple branchstories B0, B1 and B2 between a point X of branch from a preceding mainstory A and a point Y of connection to a succeeding main story C.Suppose that the recorded states between the point X of branch and thepoint Y of connection on a recording medium are arranged as shown inFIG. 13B. Suppose that the branch story B0 is played back as shown inFIG. 13C. Then, the playback apparatus must jump from one cell toanother for playback. Actually, the pickup will perform processing whilereading data and validating the read data.

Suppose here that each branch story is divided into m cells. Then, theplayback interval (jump distance) of the story that is the shortest as awhole, B0 in this example, will be the longest. Thus, consideration isgiven to the shortest story.

If the whole capacity of B0 is taken as V0, then the capacity of onecell in B0 will be V0/m.

Next, the playback time Tp for B0-0 is given by

    Tp=(V0/m)/Pr

and the read time Tr for BO-0 is given by

    Tr=(V0/m)/Rr

where Pr is the maximum code playback rate per unit time of the playbackapparatus and Rr is the read rate of the playback apparatus.

At the time of playback of B0, the amount of coding Vj over which a jumpis to be made is represent by ##EQU1## where i represent story numbersand M represents the number of stories.

The jump time Tjp at the time of playback of B0 is represented by##EQU2## where Jp is the amount of coding over which the playbackapparatus can jump.

When it is made a condition that the jump time required for jump to thenext cell is shorter than the playback time, i.e., Tp-Tr>Tjp, thefollowing expression can be obtained ##EQU3## The number of divisions isset in accordance with expression (1).

The points of division for obtaining the cells should be determinedaccording to the format of data so that no disturbance will occur inreproduced data. Thus, there is no need of dividing strictly by rote soas to meet the above condition only. For example, in a video program inwhich compressed video data, compressed sound data and compressedsubvideo data are time-division multiplexed, time division points shouldbe made cell division points. The cells contain compressed video data,compressed sound data, and compressed subvideo data. Further, in thecase of coded video data compressed by the MPEG2 system, the data ispreferably divided in units of a group of pictures (GOP) having aplayback time of the order of 0.4 to 0.5 seconds.

The invention is not restricted to the above description and can beimplemented and modified in various ways. The above description is oneof the basic principles of the invention.

If each cell has its identification number and the next cell'sidentification number appended, it becomes convenient to handle atplayback time. To handle the cells, management information in which theorder in which the cells are played back has been set up is utilized inthe control unit of the playback apparatus. To increase datareliability, each cell may contain an error correcting code that permitscorrection processing to be concluded in it. In the examples of FIGS. 7and 8 in which the cells of the respective branch scenes aretime-division multiplexed, the first to n-th scene cell blocks arearranged in sequence and each scene cell block is made up by cells fromdifferent branch scenes. In this case, each scene cell block may containan error correcting code that is inconcluded in it.

In the invention, the division of each branch scene into cells and thearrangement of the cells of the respective branch scenes on atime-division multiplexing basis can be described roughly as follows.

That is, the cells are divided and then arranged time-divisionmultiplexed so as to meet the condition that Tp>Ts where Tp is theactual playback time required for the reproduction circuit to play backa video unreproduced portion of a reproduce cell read by the pickup ofthe playback apparatus and Ts is the read time required for the pickupto search for and read the next cell succeeding that reproduce cell. Inthis case, the playback time by the playback circuit of the playbackapparatus is determined by the capacity of a buffer memory for storingreproduced signals, the amount of data multiplied by the compressionrate, and the read clock frequency, and the read time is determined as aparameter consisting mainly of the response speed of the pickup.

In the optical disk, multiple branch scenes between the point of branchand the point of connection are recorded in the form such that each ofthe branch scenes is divided into cells each corresponding to apredetermined video playback time and cells that are to be played backsuccessively are placed within a distance corresponding to apredetermined amount of coding. Suppose here that, in the playbackapparatus, the time required to seek the distance corresponding to thepredetermined amount of coding is Ts, the amount of read data per unittime is Rr, and the maximum amount of coding per unit time dissipatedfor video playback is Pr. Then, the time Ts and the time Tc required forthe playback apparatus to decode one cell by means of a decoder andprovide a video reproduced output are related by

    Tc-[(Tc×Pr)/Rr]>Ts

FIG. 14 shows an arrangement of the playback apparatus for playing backthe above-described information recording medium (optical disk).

A disk 100 is placed on a turntable 101 driven by a motor 102 to rotate.In playback mode, information recorded on the disk 100 is picked up by apickup unit 103. The pickup unit 103 is subject to movement control andtracking control by a pickup driver 104. An output of the pickup unit103 is entered into a demodulator 201 for demodulation. The demodulateddata is entered into an error correcting unit 202 for error correctionand then into a demultiplexer 203 through a butter memory 220. Thedemultiplexer 203 separately derives video information, caption and textinformation, sound information, control information, etc. That is,caption and character information (subpicture), sound information andthe like are recorded on the disk 100 to correspond with videoinformation. In this case, as caption and character information andsound information, a choice can be made from various languages under thecontrol of a system controller 204.

To the system controller 204 is applied a user operation input via anoperating unit 205.

The video information separated by the demultiplexer 203 is entered intoa video decoder 206 where it is subjected to a decoding processcorresponding to the type of a display unit. For example, it isconverted to meet NTSC, PAL, SECAM, wide screen, or the like. Thesubpicture separated by the demultiplexer 203 is entered into asubpicture processor 207 where it is decoded into a caption andcharacter video. A video signal decoded by the picture decoder 206 isentered into an adder 208 where it is added to the caption and charactervideo (subpicture). The adder output is applied to an output terminal209. The sound information selected and separated by the demultiplexer203 is entered into an audio decoder 211 where it is demodulated andthen applied to an output terminal 212. In addition to the audio decoder211, the audio processing unit includes an audio decoder 213, which canreproduce voice in another language and apply it to an output terminal214.

The buffer memory 220 is provided to follow the error correcting unit202. The reproduced data is temporarily stored in the buffer memory 220and then applied to the multiplexer 203 according to the decoding speed.When the buffer memory 220 overflows with data in normal continuousplayback, the system controller 204 performs kickback processing. Thekickback processing is to read data for predetermined sectors read sofar again and is a function of compensating for the loss of data whenthe buffer memory 220 overflows with data.

When an optical disk containing multiple stories is played back, a listof options for the multiple stories, serving as disk managementinformation, is displayed as a menu on, for example, the monitor screenor the system subdisplay unit. The user is allowed to make a choiceamong the multiple stories in advance through the remote-controloperating unit 205 while watching the menu.

Upon receipt of option information, the system controller 204 graspsidentification information of the branch story and extracts from thebuffer memory 220 data with the header to which the identificationinformation is attached and applies it to the demultiplexer 203.

As described above, according to the invention, data for multiplestories or scenes are recorded on a recording medium so as to allow thephysical distance the pickup moves at playback time to be short,preventing a break or disturbance in reproduced video from occurring.

Next, an optical display playback system to which the invention isapplied will be described specifically.

First, the kind of information is recorded as information related to theinvention on an optical disk will be described.

FIG. 15 shows volume space on the optical disk 100. As shown in FIG. 15,the volume space consists of a volume and file configuration zone, a DVDvideo zone, and other zones. In the volume and file configuration zoneis described a UDF (Universal Disk Format Specification Revision 1.02)configuration, the data of which can be read by any computer that meetsa predetermined standard. The DVD video zone has a video manager (VMG)and a video title set (VTS). The video manager (VMG) and the video titleset (VTS) each consist of multiple files. The video manager (VMG) isinformation for controlling the video title set (VTS).

In FIG. 16 there is illustrated in more detail the structures of thevideo manager (VMG) and the video title set (VTS).

The video manager (VMG) has video manager information (VMGI) as controldata and a video object set (VMGM₋₋ VOBS) as data for menu display.Also, backup video manager information (VMGI) that is identical incontent to the VMGI is included.

The video title set (VTS) contains video title set information (VTSI) ascontrol data, a video object set (VTSM₋₋ VOBS) as data for menu display,and a video object set (VTSTT₋₋ VOBS) for the title of a video title setthat is a video object set for video display. Also, backup video titleset information (VTSI) that is identical in content to the VMGI isincluded.

The video object set (VTSTT₋₋ VOBS) for video display is made up bymultiple cells. Each cell is assigned a cell identification number.

FIG. 17 illustrates a relationship between the video object set (VOBS)and the cells and the contents of the cells hierarchically. When DVDplayback processing is performed, video breaks (scene changes, anglechanges, story changes, etc.) and special playback are handled in unitsof cells (Cell), or in units of video object units (VOBU) that are in alayer below the cells, or in units of interleaved units (ILVU).

First, the video object set (VOBS) comprises multiple video objects(VOB₁₃ IDN1 to VOB₁₃ IDNi). Moreover, one video object comprisesmultiple cells (C₋₋ IDN1 to C₋₋ IDNj). Furthermore, one cell (Cell)comprises multiple video object units (VOBU) or interleaved units thatare described later. One video object unit (VOBU) comprises onenavigation pack (NV₋₋ PCK), multiple audio packs (A₋₋ PCK), multiplevideo packs (V₋₋ PCK), and multiple subpicture packs (SP₋₋ PCK).

The navigation pack (NV₋₋ PCK) is mainly used as control data forcontrol of reproduced display of data in the video object unit to whichit belongs and control data for search for data in the video objectunit.

The video pack (V₋₋ PCK) is main video information, which is compressedin accordance with the MPEG standard or the like. The subpicture pack(SP₋₋ PCK) is subvideo information having contents that are auxiliary tomain video. The audio pack (A₋₋ PCK) is sound information.

FIG. 18 shows an example of controlling the order of playback of thecells (Cells) by a program chain (PGC).

As the program chain (PGC), various program chains (PGC#1, PGC#2, PGC#3,. . . ) are prepared so as to allow the order of playback of data cellsto be set variously. Therefore, the order of playback of cells will beset by making a choice among the program chains.

An example in which program #1 to program #n described by program chaininformation (PGCI) are executed is shown. The program shown has thecontents to specify a cell specified by (VOB₋₋ IDN#s, C₋₋ IDN#1) andsubsequent cells within the video object set (VOBS) in turn.

The program chain, recorded on the management information recording areaof the optical disk, is information that is read prior to the reading ofthe video title set of the optical disk and then stored in the memory inthe system controller. The management information is placed at thebeginning of the video manager and each video title set.

FIG. 19 shows a relationship between a video object unit (VOBU) andvideo packs in it. Video data in VOBU comprises one or more GOPs.Encoded video data conforms to ISO/IEC13818-2 by way of example. The GOPin VOBU comprises an I-picture and a B-pictures and the continuation ofthis data is divided into video packs.

Next, a description is given of a data unit when multi-angle informationis recorded and reproduced. When multiple scenes that differ in point ofview for a subject are recorded on an optical disk, an interleaved-blockportion is built on recording tracks to perform seemless playback. Inthe interleaved block portion, multiple video objects (VOB) that differin angle are each divided into multiple interleaved units. As describedpreviously, the interleaved units are recorded in such an arrangement asallows seemless playback.

In the previous description, the multiplexing of multiple stories on atime division basis was described. In the description, all of thedivided blocks were termed cells. In the subsequent description,interleaved blocks, in particular, shall be called interleaved units.

FIG. 20 shows an example of an arrangement of interleaved blocks. Inthis example, 1 to m video objects (VOB) are each divided into ninterleaved units and arranged. Each video object (VOB) is divided intoan equal number of interleaved units. Thus, this corresponds to theexample of FIG. 7 in the previous description.

FIG. 21 shows a recorded state in which, for example, two VOBs, or videoobjects for angle-1 and angle-2 scenes, are each divided into threeinterleaved units (ILVU1-1 to ILVU3-1) (ILVU1-2 to ILVU3-2) and arrangedon one track and an example of a reproduced output of the angle 1. Inthis example, the angle-2 information is not captured.

FIG. 22 shows the playback apparatus shown in FIG. 14 in a simplifiedform. When such jump playback as described above is performed, it isrequired to supply a decoder 206 with data without interruption. To thisend, a track buffer 220 is provided. Vr represents the transfer rate ofdata sent from an error correcting unit 220 to the track buffer 220, andVo represents the transfer rate of data sent from the track buffer 220to the decoder. Data is read from the disk with each error correctingblock. One error correcting block corresponds to 16 sectors.

FIG. 23 shows the case where an increase and a decrease in data enteredinto the buffer when an interleaved block is played back is the worst.In this case, the interleaved unit on the recording track is jumped andthe read and playback processing of data in an interleaved unit to whichjump is made is carried out.

In the figure, Vr represents the transfer rate of data sent from theerror correcting unit 202 to the track buffer 220, and Vo represents thetransfer rate of data sent from the track buffer 220 to the decoder.

Tj is the jump time and includes the track seek time and the necessarytime incident to the track seek (latency time). b represents the datasize of one ECC block (for example, 261114 bits). Te represents the timerequired to read one ECC block into the buffer. Bx represents the amountof data left in the buffer 220 at the start of the jump (time t4).

The curve indicating the amount of data in FIG. 23 shows that data isstored into the buffer 220 at a storage rate of a gradient of (Vr-Vo)from time t2. Also, the curve shows that the amount of data in thebuffer reaches zero at time t6. The data in the buffer decreases at arate of reduction of gradient -Vo and reaches zero at time t6.

It is the following that can be understood from that curve. That is, thecondition that data is continuously output from the buffer 220, or thecondition that data is applied to the decoder without interruption is

    Bx≧Vo(Tj+3Te)                                       (2)

The condition of the interleaved unit size (ILVU₋₋ SZ) that

    ILVU.sub.-- SZ≧{(Tj×Vr×10.sup.6 +2b)/ (2048×8)}×Vo/(Vr-Vo)                          (3)

can be derived.

This expression is equivalent to expression (1) and the number m ofinterved units is merely eliminated. That is, ##EQU4## (V0/m) inexpression (1) corresponds to the size of an interleaved unit, Pr to Vo,and Rr to Vr.

The right-hand side of expression (1) is the jump time. In expression(3), the number of sectors corresponding to the jump time is expressedstrictly as

    {(Tj×vr×10.sup.6 +2b)/(2048×8)}.

An attempt is made to change expression (1) so that it will be madeclose to expression (3). By setting (V0/m)=USZ as unit size, Pr=Vo,Rr=Vr, and the right-hand side of equation (1)=Tjp, expression (1) canbe changed as follows:

    USZ×(1/Vo)-USZ×(1/Vr)≧Tjp

    USZ×{(1/Vo)-(1/Vr)}≧Tjp

    USZ×{(Vr--Vo)/(V0 Vr)}≧Tjp

    USZ≧Tjp×Vr×{(Vo)/(Vr-Vo)}               (4)

Expression (4) has its dimension represented by the amount of data andis in the form in which elements of 10⁶ and 1/(2048×8) in expression (3)are omitted. Tjp corresponds to Tj+2b.

How much capacity is needed for the buffer memory will be investigatednext. It is preferable that the capacity of the buffer memory be suchthat output data of the memory is not interrupted even when the playbackapparatus performs a kickback operation and subsequently makes a jumpover an interleaved units. The kickback is the state where the pickupwaits for reading while the disk makes one rotation and is to shift thereading position to the adjacent track after one rotation of the disk.

FIG. 24 shows the time when the playback apparatus performs a kickbackoperation and subsequently performs the maximum jump operation and thestate where data in the buffer memory decreases.

Bm=size of the track buffer

Tk=kickback time (corresponding to one rotation time of the disk).

Te=read-in time for one ECC block (24 msec).

Tj=jump time=track seek time (tj)+latency time (=Tk)

MAX₋₋ Vo=maximum read-out rate for one LVU

The capacity of the buffer memory that ensures the succession of datawhen the playback apparatus performs a kickback operation andsubsequently performs the maximum jump operation is given, in the abovecondition, by

    Bm≧{(2Tk+tj+4Te)×MAX.sub.-- Vo×10.sup.6 }/(2048×8)

The unit of Bm is sector, the unit of each of Tk, tj and Te is thesecond, and the unit of MAX₋₋ Vo is the Mbps.

From the above, the track buffer size required depends on Tk, tj and Teof the playback apparatus, and tj depends on the performance of seekoperation. Tk and Te depends on the rotational speed of the disk.

FIG. 25 shows examples of designs for the minimum capacity (Bm) of thetrack buffer, the kickback and seek time, the jump distance, and theamount of data per unit time output from the track buffer in playbackapparatus that plays back a digital video disk.

Next, a description will be given of the above-described interleavedunits and management information used for playing back the interleavedunits.

FIG. 26 shows video title set information (VTSI) in video title set(VTS). A video title set program chain information table (VTS₋₋ PGCIT)is described in the video title set information (VTSI). Thus, when avideo object set (VOBS) in one video title set (VTS) is played back, aprogram chain is utilized which is specified by the producer or selectedby the user from multiple program chains presented in the video titleset program chain information table (VTS₋₋ PGCIT).

In the VTSI, the following data are further described.

VTSI₋₋ MAT is a video title set information management table, in whichthe kinds of information present in this video title set and thestarting and ending addresses of each item of information are described.

VTS₋₋ PTT₋₋ SRPT is a video title set part-of-title search pointertable, in which entry points of titles and the like are described.

VTSM₋₋ PGCI₋₋ UT is a video title set menu program chain informationunit table, in which a menu of video title sets is described in variouslanguages. Thus, the menu allows the user to determine what kind ofvideo title set is described and what style of order playback can beperformed in.

VTS₋₋ TMAPT is a video title set time map table, in which information onthe recorded position of each VOBU is described which is managed withineach program chain and indicated at regular intervals of seconds.

VTSM₋₋ C₋₋ ADT is a video tile set menu cell address table, in which thestarting and ending address of each cell comprising the video title setmenu and the like are described.

VTSM₋₋ VOBU₋₋ ADMAP is a video title set menu video object unit addressmap, in which the starting addresses of menu video object units aredescribed.

VTS₋₋ C₋₋ ADT is a video title set cell address table, in which celladdress information is described.

When a program chain is selected in the playback apparatus, the order ofplaying back cells is set by that chain. In playback, NV₋₋ PCK includedin the video object unit is referred to.

NV₋₋ PCK has information for controlling display contents and displaytiming and information for data search. Thus, the retrieval and decodingof V₋₋ PCK are performed on the basis of information in the NV₋₋ PCKtable. In addition, another pack is retrieved and decoded, in which caseA₋₋ PCK and SP₋₋ PCK in a language specified by the producer or user areretrieved.

FIG. 27 shows the contents of the video title set program chaininformation table (VTS₋₋ PGCIT). In this table are described video titleset PGCI table information (VTS₋₋ PGCITI), search pointers (VTS₋₋ PGCI₋₋SRP#1 to #n) for video title set program chain information, and specificprogram chain information (VTS₋₋ PGCI).

In (VTS₋₋ PGCITI) are described the number of search pointers and theending address of this table.

In (VTS₋₋ PGCI₋₋ SRP#1 to #n) are described, as the category of thevideo tile set program chain, the number of titles in a video title setthat becomes a target, whether the program chain ends with one block orcontinues into a chain in another block, etc. In addition, the startingaddress of the video title set program chain is described in terms ofthe relative address to the starting position of this table.

FIG. 28 describes the contents of program chain information (PGCI).

The PGCI contains program chain general information (PGCI₋₋ GI), aprogram chain command table (PGC₋₋ CMDT), a program chain program map(PGC₋₋ PGMAP), cell playback information (C₋₋ PBI), and cell positioninformation table (C₋₋ POSIT).

In the PGCI₋₋ GI are described the number of programs and the number ofcells for this program chain (this information is called PGC contents(PGC₋₋ CNT)). In addition, all the playback times that the program chainintends are shown (this information is called PGC playback time (PGC₋₋PB₋₋ TM)). Moreover, a code of whether a program played back by thisprogram chain allows user operation, for example, whether the switchingof angles is possible, is described (this information is called PGC useroperation control (PGC₋₋ UPR₋₋ CTL)). Furthermore, codes of whetheraudio streams can be switched and what type of audio stream (e.g.,linear PCM, AC-3, MPEG or the like) can be switched into are alsodescribed (this information is called PFC audio stream control table(PGC₋₋ AST₋₋ CTLT)). In addition, codes of whether subvideos can beswitched and what type of subvideo (e.g., a different aspect ratio) canbe switched into are described (this information is called PGC subvideostream control table (PGC₋₋ SPST₋₋ CTLT)).

Moreover, in this PGCI₋₋ GI, the next program chain number and theprevious program chain number are also described. Furthermore, whetherthe program intended by this program chain is intended for continuousplayback, random playback, or shuffle playback is also described (thisinformation called PGC navigation control (PGC₋₋ NV₋₋ CTL)). Inaddition, color specification is performed to indicate what colorssubvideo is to be displayed in (this information is called PGC subvideopalette (PGC₋₋ SP₋₋ PLT)).

Also, the starting address of the program chain command table (PGC₋₋CMDT₋₋ SA), the starting address of the program chain program map (PGC₋₋PGMAP₋₋ SA), the starting address of the cell playback information table(C₋₋ PBIT₋₋ SA) and the starting address of cell position information(C₋₋ POSI₋₋ SA) are described.

In the program chain command table are described the pre-commands andpost-commands of the program chain and cell commands. The pre-commandsare ones to be processed prior to the execution of the program chain andthe post-commands are ones to be processed after the execution of theprogram chain. The pre-commands and post-commands are used to define thevideo title, the reproduced state of audio, and the reproduced stream onthe basis of commands or parameters decided in advance on the playerside or the disk producer side. The cell commands are ones to beprocessed subsequent to the execution of playback processing of cells.

In the starting address of the program chain program map (PGC₋₋ PGMAP),the structure of a program for which the program chain is intended isindicated and entry cell numbers of an existing program are described.

In the cell playback information table (C₋₋ PBIT) is describedinformation indicating the order of playing back cells for which theprogram chain is intended.

FIG. 29 shows cell playback information (C₋₋ PBIT) and its contents. TheC₋₋ CAT is cell attribute information and indicates the mode of a cellblock. The mode of a cell block indicates whether the cell is the firstone or the last one. Are also included information as to whetherseemless playback is to be performed, information as to whether the cellblock is among interleaved blocks, and information about seemless angleswitching. The information about seemless angle switching indicates thatthe angle switching can be made either seemlessly or non-seemlessly.

C₋₋ PBTM indicates the cell playback time, C₋₋ FVOBU₋₋ SA the startingaddress of the first video object unit (VOBU) of the cell, C₋₋ ILVU₋₋ EAthe ending address of the first interleaved unit (ILVU) of the cell, C₋₋FVOBU₋₋ SA the starting address of the last video object unit (VOBU) ofthe cell, and C₋₋ FVOBU₋₋ EA the ending address of the last video objectunit (VOBU) of the cell. The addresses are described in terms of logicalblock numbers relative to the first logical block of VOBS to which thecell belongs.

By referring to the cell playback information, a determination can bemade of whether the current playback state reaches the end of a cell.When the next cell is played back, the next cell playback information inthe cell playback information table is referred to determine thestarting address of the first VOBU of the next cell (or interleavedunit).

FIG. 30 shows the contents of the cell position information table (C₋₋PSIT). The cell position information includes the ID number of a videoobject (C₋₋ VOB₋₋ IDN) in which the cell is contained and the cell IDnumber (C₋₋ IDN) of the cell.

As described above, the management information describes cell playbackinformation, in which there is cell attribute information indicatingwhether interleaved units for multiple angles or the like have beenrecorded.

When a multi-angle video or a multi-story video is recorded, theplayback apparatus needs to switch from the angle being played back tothe other or switch from the story being played back to the otheraccording to user's operation. In this case, the playback apparatusresponds to the user's operation on the basis of the followinginformation. First, the structure of a pack will be described.

FIG. 31 shows the formats of one pack and one packet. One pack comprisesa pack header and a packet. In the packet header are described a packstart code, a system clock reference (SCR), etc. The pack start code isone indicating the beginning of the pack, and the system clock reference(SCR) is information indicating to the entire playback apparatus thereference time in the playback elapsed time. One pack is 2048 bits longand defined and recorded as one logical block on an optical disk.

One packet comprises a packet header and video data or audio data orsubpicture data, or navigation data. Stuffing may be provided in thepacket header. Padding may be provided in the data division of thepacket.

FIG. 32 shows the NV₋₋ PCK (see FIG. 17). The NV₋₋ PCK includes apicture control information (PCI) packet basically adapted to controldisplay pictures and a data search information (DSI) packet existing inthe same video object. In each packet are described a pack header and asubstream ID, followed by data. In each pack header is described astream ID, indicating NV₋₋ PCK. The substream ID is used to distinguishbetween PCI and DSI. In each pack header are described a packet startcode, a stream ID and the packet length, followed by data.

The PCI packet is navigation data for changing display contentssynchronously with the playback of video data in a video object unit(VOBU) to which the NV packet belongs.

In the PCI packet are described PCI general information (PCI₋₋ GI) thatis general information, non-seemless angle information (NSML₋₋ ANGLI),highlight information (HLI) and recording information (RECI) that isrecorded information.

In the PCI₋₋ GI is described PCI general information, which includes:the logical block number (NV₋₋ PCK₋₋ LBN) that is the address of thenavigation pack, the video object unit category (VOBU₋₋ CAT) indicatingthe attribute of a video object unit (VOBU) managed by the PCI, the useroperation control (VOBU₋₋ UPO₋₋ CTL) that is user operation inhibitinformation in the display period of the video object unit managed bythe PCI, the video object unit display starting time (VOBU₋₋ S₋₋ PTM),and the video object unit display ending time (VOBU₋₋ E₋₋ PTM). Thefirst picture specified by the VOBU₋₋ S₋₋ PTM is an I-picture in theMPEG standards. Further, video object unit sequence end presentationtime (VOBU₋₋ SE₋₋ E₋₋ PTM) indicating the display time of the last videoin the video object unit, the cell elapsed time (C₋₋ EITM) indicatingthe display elapsed time relative to the first video frame in a cell andso on are also described.

The NSML₋₋ ANGL indicates the destination address when an angle changeis made. That is, the video object unit includes pictures shot fromdifferent angles. The address of a VOBU is described to which atransition is made for the next playback when the display of picturesshot from a different angle from the current one is specified by theuser.

The HLI is information for specifying a specific rectangular area on thescreen and changing the brightness of that area or the color of subvideodisplayed therein. The information includes highlight generalinformation (HL₋₋ GI), a button color information table (BTN₋₋ COLIT)used when the user makes a selection among buttons for color selection,and button information table (BTNIT) for select buttons.

The RECI is information about video, audio and subpicture recorded inthe video object unit, each item of information describing what data tobe decoded is like. For example, a country code, a copyright owner codeand the date of recording are included.

The DSI packet is navigation data for making a search for a video objectunit.

In the DSI packet are described DSI general information (DSI₋₋ GI),seemless playback information (SML₋₋ PBI), seemless angle information(SML₋₋ AGLI), video object unit search information (VOBU₋₋ SRI), andsync information (SYNCI).

As shown in FIG. 33, in the DSI₋₋ GI is described the followinginformation: a system clock reference indicating the reference time forstarting decoding the NV₋₋ PCK (NV₋₋ PCK₋₋ SCR), the logical address ofthe NV₋₋ PCK (NV₋₋ PCK₋₋ LBN), the ending address of the video objectunit to which the NV₋₋ PCK belongs (VOBU₋₋ EA), the ending address ofthe first reference picture (I-picture) to be decoded first (VOBU₋₋1STREF₋₋ EA), the ending address of the second reference picture(P-picture) to be decoded first (VOBU₋₋ 2NDREF EA), the ending addressof the third reference picture (B-picture) to be decoded first (VOBU₋₋3NDREF₋₋ EA), the ID number of the VOB to which the DSI belongs (VOBU₋₋VOB₋₋ IDN), the ID number of the cell to which the DSI belongs (VOBU₋₋C₋₋ IDN), and the cell elapsed time indicating the elapsed time relativeto the first video frame in the cell (C₋₋ ELTM).

As shown in FIG. 34, in the SML₋₋ PBI is described the followinginformation: video object unit seemless category indicating whether theVOBU to which the DSI belongs is an interleaved unit (ILVU) or a preunit(PREU) that is the criterion for indicating the connection between videoobjects, the ending address of the interleaved unit (ILVU₋₋ EA), thestarting address of the next interleaved unit (ILVU₋₋ SA), the size ofthe next interleaved unit (ILVU₋₋ SZ), the video display starting timein the video object (VOB) (VOB₋₋ V₋₋ S₋₋ PTM), the video display endingtime in the video object (VOB) (VOB₋₋ V₋₋ E₋₋ PTM), the audio stoppingtime in the video object (VOB) (VOB₋₋ A₋₋ STP₋₋ PTM), and the audio gaplength in the video object (VOB) (VOB₋₋ A₋₋ GAP₋₋ LEN). The preunit(PREU) is the last unit in a BOVU immediately before the interleavedunit.

In the video object unit seemless category (VOBU₋₋ SML₋₋ CAT) arefurther described a flag indicating whether or not the interleaved unitis one at the starting time and a flag indicating whether theinterleaved unit is one at the ending time.

FIG. 35 shows the contents of the seemless angle information (SML₋₋AGLI). C1 to C9 indicate the number of angles. Even if a maximum of nineangles exists, the addresses and sizes of their destination interleavedunits can be indicated. That is, the addresses and sizes (SML₋₋ AGL₋₋Cn₋₋ DSTA) (n=1 to 9) of interleaved units that are destinations for therespective angles are described. When the user performs an operation ofchanging the angle while watching video, this operation information isreferenced to, thereby allowing the playback apparatus to recognize theplayback position of the next interleaved unit.

FIG. 36 shows VOBU search information (VOBU₋₋ SRI) which is referencedto at the time of special playback, etc.

The information describes the starting addresses of VOBUs (0.5×n)seconds before and after the starting time of the current video objectunit (VOBU). That is, the starting address of each of +1, +20, +60, +120and +240 VOBUs as forward addresses (FWDINn) and a flag that a videopack is present in the unit are described according to the order ofplayback with the VOBU containing the DSI being referenced to. Thestarting address is described in terms of the number of logical sectorsrelative to the leading logical sector in the VOBU. The use of thisinformation permits VOBUs the user wants to play back to be selectedoptionally.

FIG. 37 shows sync information. In this sync information are describedthe address of an object audio pack to be synchronized and the VOBUstarting address of an object subvideo pack to be synchronized.

The above-described management information is described on an opticaldisk. The system controller of the playback system makes a reference tothe program chain information in the video manager to thereby acquirecell playback information. By referring to the cell attributeinformation, whether interleaved unit blocks for multiple angles havebeen recorded is recognized. When the interleaved unit blocks have beenrecorded, seemless playback information and seemless angle informationin the NV₋₋ PACK are acquired and stored in the buffer memory in themiddle of playback. When angle switching information is entered by theuser, the seemless angle information is referenced to, whereby theplayback of interleaved units for the angle specified by the user isstarted. Then, reference is made to the seemless cell playbackinformation contained in the acquired NV₋₋ PAC to recognize theinterleaved unit to be played back next. By referencing to the cellplayback information, a decision can be made as to whether it is the endof a cell that is currently played back. To play back the next cell,reference is made to the next cell playback information in the cellplayback information table to determine the starting address of thefirst VOBU of the next cell (or interleaved unit).

The system controller 204 of the playback apparatus shown in FIG. 14 isequipped with means for processing various items of managementinformation, program chains, navigation packs, etc., as described aboveand processing operation inputs from the remote control operating unit205. Thus, detecting means for detecting cell attribute information,cell playback sequence information and branch scene switchinginformation (angle information and the like) are provided. And referenceis made to information stored in the detecting means in response to anoperation input to thereby determine an interleaved unit stream to beplayed back. In this case, by controlling the tracking controller in thepickup unit 103 and the timing of reading of data by the errorcorrecting unit 202, kickback and jump processing is implemented.

The invention can be applied to the manufacture and sale of opticaldisks in multimedia and the manufacture and sale of optical diskrecording and playback apparatuses.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, representative device andillustrated examples shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

We claim:
 1. A recording disk comprising:a data area storing recordeddata to be decoded, reproduction control data, and a multi-scene videoprogram having a plurality of optionally selectable branch scenesrecorded in recording tracks, said plurality of branch scenes beingdivided as interleaved units at a branch point where switching from onescene to another is allowed, each of said interleaved units including aplurality of video packets obtained by compressing video data in theform of packets and a plurality of audio packets obtained by compressingaudio data in the form of packets, each of said interleaved unitsfurther including a navigation pack located at a start position, saidnavigation pack having addresses and sizes of next interleaved units forthe branch scenes and serving as said control data, the interleavedunits corresponding to the respective branch scenes being recorded onrecording tracks in a physically mixed state and being readable, thenumber of divisions of each interleaved unit being determined to satisfyat least the following formula:

    Tp>Ts,

where Tp is an actual playback time required for reproducing video datacorresponding to a reproduction interleaved unit stored in a buffer, andTs is a read time during which a pickup searches for a next interleavedunit that is subsequent to the interleaved unit being reproduced on thebasis of the addresses and reads the next interleaved unit, and saidinterleaved units being arranged in a physically-mixed state.
 2. Arecording disk according to claim 1, wherein each of said interleavedunits including at least one video object unit, said video object unitincluding said control data and at least video pack subsequent to thecontrol data.
 3. A disk playback apparatus for reproducing data from adisk which has a data area storing recorded data to be decoded,reproduction control data, and a multi-scene video program having aplurality of optionally selectable branch scenes recorded in recordingtracks,said plurality of branch scenes being divided as interleavedunits at a branch point where switching from one scene to another isallowed, each of said interleaved units including a plurality of videopackets obtained by compressing video data in the form of packets and aplurality of audio packets obtained by compressing audio data in theform of packets, each of said interleaved units further including anavigation pack located at a start position, said navigation pack havingaddresses and sizes of next interleaved units for the branch scenes andserving as said control data, said interleaved units corresponding tothe respective branch scenes being recorded on the recording tracks in aphysically mixed state and being readable, the number of divisions ofeach interleaved unit being determined to satisfy at least the followingformula:

    Tp>Ts,

where Tp is an actual playback time required for reproducing video datacorresponding to an interleaved unit stored in a buffer, and Ts is aread time during which the pickup searches for a next interleaved unitthat is subsequent to the interleaved unit being reproduced on the basisof the addresses and reads the next interleaved unit, and saidinterleaved units being arranged in a physically-mixed state, said diskplayback apparatus comprising:a pickup for reading information from thedisk; a demodulator for performing demodulating processing with respectto a read signal; means for determining addresses of thenext-interleaved units to be reproduced next, on the basis of thenavigation pack obtained from the demodulator; a searching element,operating upon receipt of operational information regarding sceneswitching, for controlling a data read position at which data is readfrom the disk through the pickup means on the basis of the addresses andsizes of the next interleaved units; and a reproducing circuit forcausing new interleaved units searched for by the searching element tobe stored in the buffer and for decoding data contained in the videopack of the new interleaved units, said disc playback apparatussatisfying at least the following formula:

    Tp>Ts,

where Tp is an actual playback time required for reproducing video datacorresponding to a reproduction interleaved unit stored in a buffer, andTs is a read time during which the pickup searches for a nextinterleaved unit.